Number

129

129 is a composite number, odd, a calendar year.

129 (one hundred twenty-nine) is an odd 3-digit number. It is a composite number with 4 divisors, and factors as 3 × 43. Written other ways, in Roman numerals it is CXXIX and in binary, 10000001.

Arithmetic Number Ascending Digits Binary Palindrome Cube-Free Deficient Number Evil Number Happy Number Pernicious Number Recamán's Sequence Semiprime Squarefree Year

Interestingness

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8 notable facts · grade A

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Historical context — 129 AD

Calendar year

Year 129 (CXXIX) was a common year starting on Friday of the Julian calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Historical context — 129 BC

Calendar year

Year 129 BC was a year of the pre-Julian Roman calendar.

Excerpt from Wikipedia (en) ↗ · Licensed CC BY-SA 4.0 Read the full article on Wikipedia →

Year facts

Year type: Common year
Standard 365-day year; not divisible by 4 (or divisible by 100 but not 400).
Days in year: 365
ISO weeks: 52
Started on: Saturday
January 1, 129
Ended on: Saturday
December 31, 129
Friday the 13ths: 1
One Friday the 13th this year.
Decade: 120s
120–129
Century: 2nd century
101–200
Millennium: 1st millennium
1–1000
Years ago: 1,897
1897 years before 2026.

In other calendars

Hebrew: 3889 / 3890 AM
Rosh Hashanah falls in September/October.
Chinese: Year of the zodiac:Earth zodiac:Snake
Sexagenary cycle position 6 of 60. Lunar new year falls in late January / mid-February.
Buddhist Era: 672 BE
Counted from the parinirvana of the Buddha (Theravada / Thai / Sri Lankan convention).
Ethiopian: 121 / 122 ET
Year boundary at Enkutatash (September 11/12).
Indian National (Saka): 51 / 50 Saka
Indian national calendar; year starts in March.

Properties

Parity: Odd
Digit count: 3
Digit sum: 12
Digit product: 18
Digital root: 3
Palindrome: No
Bit width: 8 bits
Reversed: 921
Recamán's sequence: a(142) = 129
Square (n²): 16,641
Cube (n³): 2,146,689
Divisor count: 4
σ(n) — sum of divisors: 176
φ(n) — Euler's totient: 84
Sum of prime factors: 46

Primality

Prime factorization: 3 × 43

Nearest primes: 127 (−2) · 131 (+2)

Divisors & multiples

All divisors (4)

1 · 3 · 43 · 129

Aliquot sum (sum of proper divisors): 47

Factor pairs (a × b = 129)

1 × 129

3 × 43

First multiples

129 · 258 (double) · 387 · 516 · 645 · 774 · 903 · 1,032 · 1,161 · 1,290

Sums & aliquot sequence

As consecutive integers: 64 + 65 42 + 43 + 44 19 + 20 + 21 + 22 + 23 + 24

Aliquot sequence: 129 → 47 → 1 → 0 — terminates at zero

Continued fraction of √n

√129 = [11; (2, 1, 3, 1, 6, 1, 3, 1, 2, 22)]

Period length 10 — the block in parentheses repeats forever.

Representations

In words: one hundred twenty-nine
Ordinal: 129th
Roman numeral: CXXIX
Binary: 10000001
Octal: 201
Hexadecimal: 0x81
Base64: gQ==
One's complement: 126 (8-bit)
Scientific notation: 1.29 × 10²
As a duration: 129 s = 2 minutes, 9 seconds

In other bases

ternary (3) 11210

quaternary (4) 2001

quinary (5) 1004

senary (6) 333

septenary (7) 243

nonary (9) 153

undecimal (11) 108

duodecimal (12) a9

tridecimal (13) 9c

tetradecimal (14) 93

pentadecimal (15) 89

Palindromic in base 2, base 6

As an angle

129°

129° ≈ 2.251 rad

Compass bearing: SE (southeast)

Why does a circle have 360 degrees? →

Historical numeral systems

Babylonian (base 60): 𒁹𒁹 𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹𒁹
Egyptian hieroglyphic: 𓍢𓎆𓎆𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺𓏺
Greek (Milesian): ρκθʹ
Mayan (base 20): 𝋦·𝋩
Chinese: 一百二十九
Chinese (financial): 壹佰貳拾玖

In other modern scripts

Eastern Arabic ١٢٩ Devanagari १२९ Bengali ১২৯ Tamil ௧௨௯ Thai ๑๒๙ Tibetan ༡༢༩ Khmer ១២៩ Lao ໑໒໙ Burmese ၁၂၉

Digit at this position in famous constants

π — Pi (π): Digit 129 = 0
e — Euler's number (e): Digit 129 = 9
φ — Golden ratio (φ): Digit 129 = 6
√2 — Pythagoras's (√2): Digit 129 = 5
ln 2 — Natural log of 2: Digit 129 = 3
γ — Euler-Mascheroni (γ): Digit 129 = 1

Also seen as

Unicode codepoint

U+0081

Control character (Cc)

UTF-8 encoding: C2 81 (2 bytes).

Lookup U+0081 on Compart ↗ Lookup on FileFormat.Info ↗

Hex color

#000081

RGB(0, 0, 129)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.129.

Address: 0.0.0.129
Class: reserved
IPv4-mapped IPv6: ::ffff:0.0.0.129

Unspecified address (0.0.0.0/8) — "this network" placeholder.

Musical pitch

Heard as a frequency, 129 Hz is closest to:

Concert pitch (A4 = 440 Hz): C3 (130.8 Hz, -24¢)
Scientific pitch (C4 = 256 Hz): C3 (128 Hz, +13¢)
Baroque pitch (A4 = 415 Hz): C♯3 (130.7 Hz, -23¢)

Food additive (E-number)

On an ingredients label, E129 is Allura Red AC, a food colour.

E-number reference (Wikipedia) ↗